1. The dose of pentobarbitone required for anaesthesia was significantly greater for dystrophic hamsters than for normal animals.
2. Serum creatine kinase activity was significantly higher in dystrophic than in normal hamsters.
3. Brain, heart and tibialis anterior muscle from dystrophic animals contained significantly less creatine kinase than the normal tissues.
4. Creatine kinase in normal and dystrophic sera, as in skeletal muscles, consisted of MM isoenzyme. Heart creatine kinase consisted of both MM and MB types and brain contained only the BB isoenzyme.
5. Pentobarbitone raised serum creatine kinase activity of normal and dystrophic hamsters to the same extent, elevation of enzyme activity being dependent on the amount of pentobarbitone injected.
6. The sera of pentobarbitone-treated normal and dystrophic hamsters contained only the MM isoenzyme.